President Trump will be attending the World Economic Forum in Davos this week. Inevitably, attention will focus on whether the president projects a commitment to internationalist values or reiterates his truculent nationalism in the name of making America “great again.” Attention will also focus on the durability of the current economic and market upswing that has buoyed the spirits of businesses and investors around the world. While Trump will probably try to take credit for all the economic good news, it is unlikely that he deserves it. He is president of the United States, not the world. And the economic...